It sounds like you have some truly wonderful experiences! 
There’s still a possibility that it could be astral travel, but perhaps you are inviting these spirit guides into your space? It’s possible to invite others (especially deities, spirits, ancestors, or others you have a connection with) into your personal world, or, like dreams, your deeper conscious may also step in to help craft wonders alongside your conscious mind. Could be a possibility! 
You know, the more I think about visualizations vs. astral travel, the more I realize just how hard it can be to tell them apart! This is a great area to explore - thank you for opening up this discussion, Katharina! 
That’s really neat! Do you think you may have crafted an Inner Temple? It’s a great way to cast spells or practice, no matter where your physical body is.
That’s awesome! It sounds like you have a natural knack for lucid dreaming Again, I wouldn’t say I’m an expert, but I went through a period in my Craft where I was training for lucid dreaming and found there are a bunch of strategies, visualizations, and methods to try. I found that having some kind of marker worked for me - it involved choosing an item and asking myself if I was dreaming whenever I saw it (both awake and asleep). It becomes a habit that works in the dream world, and can be a key to realizing you’re asleep, which can then lead to lucidity.
I’ve drifted away from my training (too many other things to study!), but there are plenty of resources around! If you’re interested in lucid dreaming, you may find this discussion helpful:
It’s an older book that may not be up to date on recent discoveries in the fields of sleep and dreams, but I enjoyed Lucid Dreaming Plain and Simple by Robert Waggoner.
I hope others will have some additional astral travel and lucid dreaming book recs for you!
Good luck and blessed studies 
